Human response to noise is subjective and can
vary greatly from person to person. Factors that can influence
individual response include: intensity, frequency, and time
pattern of the noise; the amount of background noise present
prior to the intruding noise; and the nature of work or human
activity that is exposed to the noise. The adverse effects of
noise include interference with concentration, communication and
sleep. At the highest levels, noise can induce hearing damage.

The unit of measurement of environmental noise
is the decibel (dB). To better approximate the range of
sensitivity of the human ear to sounds of different frequencies,
the A-weighted decibel scale was devised. Because the human ear
is less sensitive to low-frequency sounds, the A-scale
de-emphasizes these frequencies by incorporating frequency
weighting of the sound signal. When the A-scale is used, the
decibel levels are shown as dBA. On this scale, the range of
human hearing extends from about three dBA to about 140 dBA. A 10
dBA increase is perceived by most people as a doubling of the
sound level. The smallest change that can be heard is about two
to three dBA. Some representative noise sources, their associated
dBA noise levels, and corresponding effects are shown in Figure 4.10.1.

Environmental noise levels typically fluctuate
over time, and different types of noise descriptors are used to
account for this variability. Useful noise descriptors measure
time-averaged noise levels; these descriptors include the
energy-equivalent noise level (Leq)(1) and the Community Noise Equivalent Level (CNEL)(2).
The Leq is the actual
time-averaged noise level, while CNEL is a 24-hour,
"weighted" noise level which accounts for greater
sensitivity of most people to evening and nighttime noise. The
CNEL noise descriptor is commonly used in establishing noise
exposure guidelines for specific land uses. In this report, noise
levels reported in terms of Leq or CNEL reflect "A-weighted" decibels (dBA).

Regional Setting

Noise is typically characterized as a local
condition given the fact that noise generated by a particular
source decays rapidly as distance from the source increases.
Typically, noise levels in rural and sparsely populated areas
away from major roads are below 40 CNEL. In comparison,
noise levels in developed and highly urbanized areas and/or along
busy roadways can reach 70 CNEL or more. In most areas,
automobile and truck traffic are the major source of
environmental noise. Traffic activity generally produces an
average sound level that remains fairly constant with time. Air
and rail traffic, and commercial and industrial activities are
also major sources of noise in some areas. Various noise sources
are associated with utility operations including stationary
sources, such as turbines, compressors and generators, cooling
towers, and mobile sources, such as maintenance trucks.

Federal, state, and local agencies regulate
different aspects of environmental noise. Federal and state
agencies generally set noise standards for mobile sources such as
aircraft and motor vehicles, while regulation of stationary
sources is left to local agencies. Local regulation of noise
involves implementation of General Plan policies and Noise
Ordinance standards. Local General Plans identify general
principles intended to guide and influence development plans, and
Noise Ordinances set forth specific standards and procedures for
addressing particular noise sources and activities. Each of the
12 power plants to be divested is governed by local or county
ordinances.

General Plans recognize that different types of
land uses have different sensitivities towards their noise
environment; residential areas are generally considered to be the
most sensitive type of land use for exposure to noise and
industrial/commercial areas are generally considered to be the
least sensitive. Figure 4.10.2 presents typical
noise compatibility guidelines for a variety of land uses. Local
noise ordinances typically set forth standards related to
construction activities, nuisance-type noise sources, and
industrial property-line noise levels.

Local Setting

The proposed divestiture project involves 12
Edison power plants in various locations throughout southern
California. However, the existing acoustical environment for only
those plants located within 0.5 mile of a potentially sensitive
noise receptor are discussed here. Noise from plants located more
than 0.5 mile from an existing or anticipated noise-sensitive
land use (e.g., residences, schools, hospitals, and convalescence
homes) would not be expected to affect such sensitive uses, and
therefore are not discussed below. Power plants excluded on this
basis include Cool Water, Etiwanda, Long Beach, Mandalay, and
Ormond Beach.

Descriptions of the existing ambient conditions
for the remaining eight power plants are presented below.
Additionally, the applicable local regulations for the plants
where noise is a potential issue is discussed. The types of
operating units and power output are similar for many of the
affected power plants; however, the plant layouts, the amount of
noise abatement incorporated into the plant design, and the
existing community noise environment are different at each plant,
thereby precluding general classification of the existing noise
environment around the plants.

Alamitos

The Alamitos power plant is located in the City
of Long Beach. The closest residences are located approximately
300 feet west across Studebaker Road and Los Cerritos Channel,
and approximately 500 feet north across State Route 22. Leisure
World, a large senior citizen residential development is
approximately one-quarter mile to the east. Adjacent land uses
include Los Angeles Department of Water and Powers
(LADWPs) Haynes power plant to the east across the San
Gabriel River, commercial and residential to the north,
residential to the northwest, and open space (oil field) to the
south and southwest.

Past measurements of noise levels conducted for
the City of Long Beach near the plant range from 44-49 dBA during
the day to 44-47 dBA at night (ENTRIX, 1996). Other noise
measurements in the vicinity of the project site at residences
1,000 feet west of the plant along Palo Verde Avenue registered
55 dBA in the afternoon (ENTRIX, 1996). Of the seven units at
Alamitos, only Units 4 and 7 were operating during the
measurement.

In the past, Edison has received and
investigated several noise complaints in the areas near the site.
Noise mitigation measures (e.g., construction of enclosures)
undertaken by Edison in the mid-80s have caused a substantial
reduction in noise levels from forced draft
fans. Noise surveys undertaken by Edison and Wyle
Laboratory after implementation of these noise abatement measures
indicated that no additional noise mitigation would be required
at the Alamitos plant to address community problems.

In general, noise generated by both the Haynes
power plant and the Alamitos power plant is part of the normal
background noise level in this area of Long Beach and are within
the limits set by the Citys noise ordinance. However, under
certain weather conditions (i.e., the Santa Ana Winds) the plant
noise is more audible than at any other time of the year.

The noise ordinance for the City of Long Beach
states that noise levels at residential areas should not exceed
an Leq (equivalent
energy level) of 50 dBA between the hours of 7:00 a.m. and
10:00 p.m. and 45 dBA from 10:00 p.m. to 7:00 a.m.

Sound measurements for the present study were
made in the vicinity of the plant at the residential development
300 feet west of the plant. The location of the measurement was
at the front property line of a dwelling unit on the west side of
Studebaker Road and Los Cerritos Channel and at the east end of
Marquinta Street. The sound level due to all sources as measured
at this location in the daytimewas 44 to 46 dBA. The dwelling
unit adjacent to the location is a single story residence with
brick and siding exterior, and backed up to Los Cerritos Channel;
an eight foot high block wall extends along the rear property
line.

A second daytime measurement in the vicinity of
the plant was taken at College Park Drive and Salida Avenue,
north of the plant and State Route 22. The steady sound level due
to all sources was approximately 58 dBA. The adjacent dwelling to
this location is a single story residence with stucco exterior, a
gable roof, and a five to six foot high block wall shielding the
rear yard.

On the day of the current sound measurements,
the plant noise included a distinct buzzing which was audible at
the plant gate and parking area, and was due to vapor extraction
equipment (Robey, 1997). One plant unit, that is unit 5, was
operating on that day. The typical operating condition is to have
two units in operation, that is either Unit 5 or Unit 6, and one
of the smaller units (Perry, 1997).

El Segundo

The El Segundo power plant is located west of
Vista del Mar in the City of El Segundo. The Pacific Ocean is
west of the plant, the Chevron Oil Company refinery is located to
the east; and the Los Angeles steam facility is located to the
north. Multi-family homes are approximately 2,000 feet south of
the closest power generating unit. The plant has four generating
units. The noise of one operating unit was not audible at the
closest multi-family home to the south.

The ambient noise in the residential areas is
primarily made up of traffic noise and the ocean surf. The City
of El Segundo General Plan Noise Element Existing Conditions
Report does not identify the El Segundo power plant as a
significant noise source within the city (ENTRIX, 1996). This
power plant is not a significant noise source during the day and
would not be expected to be a significant source at night.

The new draft noise ordinance for the City of
El Segundo states that noise levels caused by a source should not
exceed 5 dBA above the ambient noise levels at residential
property lines.

Ellwood

The Ellwood power plant is located at Los Armas
Road in Goleta, an unincorporated area of Santa Barbara County.
Adjacent land uses include a school approximately 200 feet to the
east, a golf course to the west and southwest, residential areas
500 feet to the north across Highway 101, and residential areas
1,000 feet to the east and southeast.

According to the noise level map in the Final
Goleta Community Plan, existing noise levels in adjacent areas
north of the project site are within the 65-69 dBA range,
and they increase as one gets closer to the Southern Pacific
Railroad tracks and Highway 101 reaching the 70-74 dBA range
(ENTRIX, 1996). As one moves away from these sources towards the
project site and southbound, the noise levels decrease. Areas to
the south, east, and west of the plant site experience noise
levels within 60-64 dBA range. Due to air emission restrictions,
this plant is limited to 200 hours of operation per year;
therefore, the noise generated by this plant affecting the nearby
sensitive uses is limited. Prevailing noise sources in the area
include traffic on Highway 101 and the railroad track; therefore,
any noise generated by the plant would be generally exceeded by
noise from these sources.

The County of Santa Barbara has established
criteria for noise exposure that require interior noise levels
within residential dwelling units to fall below 45 dBA and
exterior living areas be designed to keep noise exposure levels
below 65 dBA.

Highgrove

The Highgrove power plant is located at Taylor
Street in the City of Grand Terrace, San Bernardino County.
Adjacent land uses are mostly industrial and commercial. On the
west side of the plant are the Union Pacific and Atchison,
Topeka, and Santa Fe railroad tracks. Interstate 215 is located
1,000 feet to the west. The closest sensitive receptors are
low-density residential areas located approximately 1,000 feet to
the east and southeast of the generating plant.

Past ambient noise measurements undertaken near
the closest residential areas registered an average noise level
of 50 dBA (ENTRIX, 1996). This noise was primarily generated by
the surrounding industrial activities and distant traffic. When
the plant is operating at full capacity, the noise levels are
predicted to be approximately 50-55 dBA Leq at the closest
residential areas. The plant is currently not active, however,
and historically has been operated only during peak electrical
demand periods during daytime hours, an average of 1 day per
year. This level of operation results in limited community noise.

The City of Grand Terrace noise ordinance
defines intrusive noise in subjective and qualitative terms, and
specific noise levels are not provided. However, the County of
San Bernardino has established the following hourly noise level
performance standards for stationary sources at residential or
other noise-sensitive receivers: from 7 a.m. to 10 p.m., 55 Leq
dBA; and from 10 p.m. to 7 a.m., 45 Leq dBA.

Huntington Beach

The Huntington Beach power plant is located
along the Pacific Coast Highway in the City of Huntington Beach.
Adjacent uses include commercial to the north, open space to the
northeast, and southeast, and an open space recreational area to
the south. The closest residences are 200 feet west of the
power plant and 200 feet east of the fuel oil storage tanks.

Data available from Huntington Beach noise
monitoring stations indicate that the noise level in the power
plant locale is approximately 65 dBA Ldn (ENTRIX, 1996). Other
noise monitoring data indicate that the noise level at the
Huntington-by-the-Sea mobile home park across Newland Street was
approximately 50 dBA and was generated by traffic on Newland
Street and the Pacific Coast Highway. The plant-generated noise
level at the mobile home park was approximately 48 dBA
(ENTRIX, 1996).

The City of Huntington Beach considers daytime
noise levels of up to 55-dBA Leq and night-time noise levels of
up to 50-dBA Leq to be compatible with residential land use.

In the current study conducted in August 1997,
a daytime sound measurement was taken on the plant site, yielding
a value of 58 dBA at an interior fence adjacent to open space on
the northeast side of the main plant buildings. On the
measurement day, Unit 1 was operating, which represents a typical
condition (Best, 1997).

In the plant neighborhood, current sound
measurements were taken at the nearest property line of the
Huntington-by-the-Sea mobile home and trailer park west of the
plant and Newland Street; the daytime measured noise level there
was 58 dBA, due to a combination of highway and plant noise. This
location was shielded to some extent visually and acoustically by
a berm at the plant boundary.

A second daytime sound measurement in the
neighborhood was made for the current study on the north side of
Hamilton Avenue and west side of Seaforth Lane, north of the
site. There are commercial buildings intervening between the
plant and this measurement location. The measurement yielded a
value of 48 dBA due to all sources. The adjacent single family
dwelling is single story with stucco exterior and gable roof and
with a block wall along the rear line adjacent to Hamilton
Avenue.

A third neighborhood sound measurement for the
current study was made in the daytime on the northeast corner at
Hula Circle and Christine Drive, northeast of the plant; some
degree of shielding for plant noise was provided by dwellings on
the south and west sides of the streets. The sound level due to
all sources was measured at 47 dBA. Adjacent single dwellings are
typically single story with stucco or brick-and-siding exterior
with a gable roof and chimney.

Redondo

The Redondo power plant is located on Harbor
Drive in the City of Redondo Beach. Current adjacent land uses
include King Harbor Marina 0.5 mile to the west across Harbor
Drive; residential to the north and east; public beach to the
northwest; and light industrial and commercial to the north,
east, and south. The closest residences are located across
Herondo Street approximately 50 feet north of the plant
fenceline. Other residences in the plant vicinity are located on
the easterly side of Catalina Avenue east of the plant, including
a tri-level condominium facility with stucco exterior, and two
wood frame one story single dwellings which are approximately 50
years old. These residences are exposed to various noise sources
including an automobile repair shop. There is a ten foot high
sound wall along the north site boundary adjacent to Herondo
Street.

Most background noise in Redondo Beach is
created by traffic on major arterials and freeways. Typical
traffic noise registers between 57 and 64 dBA. Traffic noise on
the Pacific Coast Highway has been as high as 75-80 dBA. Other
factors contributing to the noise level are horns, sirens, loud
radios, and air traffic. The Redondo power plant is also a
recognized source of noise in the Redondo Beach area.

An existing profile of the noise environment
for the Redondo power plant has been developed through field
measurements, research, and interpolation of measured noise
exposure levels (ENTRIX, 1996). Identifying individual noise
sources from measured data is difficult. Based on these data,
monitored noise levels along the eastern perimeter of the site
ranges between 54 to 62 dBA. In general, the power plant
noise becomes dominant during periods of low traffic volumes or
when moving to side streets not blocked from view of the plant. A
noise measurement was taken on December of 1989 along Herondo
Street. According to this measurement, the noise level from both
traffic and the plant noise sources was 64 dBA Leq and the plant
noise alone was approximately 56 dBA Leq.

The City of Redondo Beach General Plan noise
element, as revised, includes policies specifically addressing
stationary noise impacts of the Redondo power plant. These
policies seek to include the installation of additional noise
buffering or reduction elements in and around the plant and the
intensification of maintenance efforts within the plant to lessen
impacts of both normal frequency and low frequency noise from
stationary sources.

In addition, the Noise Element of the City of
Redondo Beach General Plan also establishes acceptable noise
levels for various land uses, with emphasis on requirements for
residential areas and those containing the most sensitive noise
receptors, such as hospitals and schools. Under Chapter 24 of the
Municipal Code, the city has established a night-time noise
standard of 50 dBA and a daytime noise standard of 55 dBA
for residential areas of the community.

There has been a history over some years of
noise complaints, response, city enforcement action, monitoring
and mitigation involving noise affecting the residences to the
east of the plant (Robey, 1997). Mitigation measures, which have
been applied primarily to Unit 7, or Units 7 and 8, have
included: enclosures for parts of the turbine generator area and
for the forced draft fans; sound walls; fan silencers; motor
silencers; insulation of ductwork; pump and exciter enclosures;
installation of a new auxiliary steam valve, and mitigation for
gas valves. A criterion level of 64 dBA at the plant east
property line has been proposed and used by Edison to predict
compliance with the city noise ordinance at the residential
facilities to the east.

Information provided in a chronology by Edison
(Robey, 1997) indicated that as of 1991 "The only
distinguishable property line noise source (that is in the
context of those affecting receptors to the east), unit 7
auxiliary steam valves, is mitigated." In the chronology,
the last item referring to enforcement action states, for 1992,
"The trial ended August 1992, in a dismissal of the charges
due to a lack of evidence. The court's ruling implied that the
noise ordinance was too difficult to interpret and enforce and
should be revised." Subsequent mitigation activities have
included Safety Relief Valve Silencers, Auxiliary Steam quiet
valves, fan active noise cancellation and SCR blower noise
enclosures.

For the current study, a daytime sound
measurement was made in the vicinity of the plant at the nearest
dwellings, that is on the north side of Herondo Street at
Monterey Boulevard. The sound level was measured at approximately
51 dBA steady level due to traffic and plant sources. The
adjacent residential building is a three story apartment building
with stucco exterior. Generating units 5, 6, 7, and 8 were
operating on the day of the sound measurements.

San Bernardino

The San Bernardino power plant is
a 90.5-acre site on San Bernardino Avenue in the County
of San Bernardino. The northern property line of the site is
adjacent to the Santa Ana River, and the eastern property line is
next to an open field. Norton Air Force Base is located north of
the plant. The residential areas closest to the plant are the
houses on the western side of Mountain View Avenue, opposite the
plant. These homes are the most sensitive noise receptors in the
vicinity of the plant. The major noise sources in the area are
Norton Air Force Base, the power plant, and the local traffic on
Mountain View Avenue.

According to property line and community noise
measurements conducted at San Bernardino power plant (ENTRIX,
1996), noise levels at the nearest residences range from 64 to 67
dBA during daytime and from 59 to 62 dBA during the nighttime,
when the plant is in operation. This plant is currently inactive,
however, and has historically been operated for 1-2 months each
year during the peak demand period in summer.

According to the County of San Bernardino
ordinance, noise levels in residential areas are not to exceed
55-dBA Leq from 7:00 a.m. to 10:00 p.m. or 45-dBA Leq from 10:00
p.m. to 7:00 a.m. The City of San Bernardino has a revised noise
ordinance that calls for noise levels at the nearest residential
receiver not to exceed 50 dBA at nighttime.

CHECKLIST ISSUES

a) Increases in Existing Noise Levels

An important part of a noise analysis is the
identification of noise-sensitive land uses that may be affected
by a project. This would include any residential properties,
schools, or other noise-sensitive land uses adjacent to the
project. As described under "Setting" above, seven of
the twelve power plants are located near a number of residential
areas and other noise-sensitive land uses.

As a general rule, noise produced by a single
generating unit varies only slightly when operated at different
load levels, meaning that a unit operating at 25%, 50% or 100% of
its maximum capacity would result in similar noise levels
(Pacific Gas and Electric, 1996). The plants would have a
tendency to operate at a higher capacity under new ownership. As
a result, although noise levels from a single operating unit are
not expected to increase during increased plant operations,
individual units may operate more often, or the frequency of
multiple units in operation simultaneously could increase, which
would increase the overall noise environment near the plants to
some degree. As mentioned previously in this section, this would
not be an impact at the power plants where no noise-sensitive
receptors are located within one-half mile of the plants (Cool
Water, Etiwanda, Long Beach, Mandalay, and Ormond Beach).

Night is the most sensitive time for noise
effects. The expected result of potential increases in generation
would be that multiple units are operated at night (two units
would be expected to produce a noise level about 3 dBA higher
than one unit). However, current information indicates that,
sometimes, multiple boilers are left on at night, but at a
somewhat lower capacity than during the daytime (which does not
affect the noise levels). Steam boilers are generally started
during daytime hours; nighttime start-ups are not expected as a
reasonably foreseeable consequence of divestiture (Weatherwax,
1997). In as much as multiple units are sometimes operated at
night under existing conditions without identified noise impacts
and within the applicable noise ordinance criteria, the operation
of multiple units at night under divestiture would not constitute
a significant impact. If multiple units operating at night
operated at higher capacity, this would also not be significant
because (as discussed earlier) noise produced by a single unit is
fairly constant over a range of loads.

Additionally, the transfer of ownership may
require relatively minor construction, which would likely be
limited to activities necessary to separate the divested
generating units from on-site transmission and distribution
equipment, ownership of which would be retained by Edison. New
construction may generate noise levels that are unacceptable to
noise-sensitive land uses. However, such noise is anticipated to
be short-term, would occur during the daytime and would cease at
the completion of the minor construction activities. Construction
activities would be subject to specific requirements in local
noise ordinances. Therefore, potential construction impacts would
not create significant effects on sensitive receptors in the
vicinity of the power plants.

Conclusion

Increased operations resulting from the project
could result in relatively small noise level increases at some
locations; these would not be significant. Accordingly,
mitigation measures are not required to be incorporated into the
project.

b) Exposure to Severe Noise

The project would not expose people to severe
noise levels at any of the 12 power plants to be divested and
their vicinity. "Severe" noise levels are generally
regarded as those levels that can produce hearing damage or other
health effects. Typically, severe noise levels are associated
with such activities as pile driving, blasting, or military jet
operations. The project would not result in the types of
activities that would produce severe noise levels.

Based on past ambient noise measurements near
Edison's power plants, noise levels emitted by these power plants
operating at full capacity were found to be approximately 50-55
dBA Leq at about 1,000 feet (Southern California Edison, 1996).
These noise levels are acceptable to sensitive receptors in the
area.

On occasion, automatic safety relief valves
that are installed on boilers at the power plants are activated
resulting in a high-pitched whistling sound that last for a short
period of time. If operations at the power plants increase from
divestiture, the frequency of these releases may increase.
However, this would not be a constant occurrence and would not be
anticipated to expose sensitive receptors to severe noise levels.

Conclusion

Although the project could increase the
occasional occurrence of automatic safety valve releases, because
these occurrences would continue to be rare, this impact would be
considered less than significant.